Open Data supplied by Natural Environment Research Council (NERC)

Aanderaa Oxygen Optodes models 3835, 4130, 4175, 3830, 3930 and 3975

The Aanderaa Oxygen Optode is based on the ability of selected substances to act as dynamic fluorescence quenchers. The fluorescent indicator is a special platinum porphyrin complex embedded in a gas permeable foil that is exposed to the surrounding water.

A black optical isolation coating protects the complex from sunlight and fluorescent particles in the water. This sensing foil is attached to a window providing optical access for the measuring system from inside a watertight titanium housing.

The foil is excited by modulated blue light, and the phase of a returned red light is measured. By linearizing and temperature compensating, with an incorporated temperature sensor, the absolute O 2 concentration can be determined. According to the manufacturer, the lifetime-based luminescence quenching principle offers the following advantages over electro-chemical sensors:

Not stirring sensitive (it consumes no oxygen)

Less affected by fouling

Measures absolute oxygen concentrations without repeated calibrations

Better long-term stability

Less affected by pressure

Pressure behaviour is predictable

Faster response time

The 3835, 4130 and 4175 models are designed to operate down to 300 m, while there are two versions of the 3830, 3930 and 3975 models, designed to operate down to 2000 m and 6000 m, respectively. The sensors fit directly on to the top end-plate of Recording Current Meter RCM 9, and other Aanderaa instruments. Sensor specifications may be viewed via the following links: Aanderaa Oxygen Optodes 3835/4130/4175 and Aanderaa Oxygen Optodes 3830/3930/3975 .

Cefas SmartBuoy data processing

This document outlines the procedures in place at Cefas in August 2005 for processing and quality assuring SmartBuoy data.

Raw data files are processed and the data move through 4 levels, starting with raw data at level 0 through to level 3, where data are fully quality-assured and expressed in appropriate units. The application of the procedures at each level result in data deemed fit to progress to the next level.

Cefas Quality Assurance (QA) Protocols

At Level 0, raw binary data files from the loggers are transferred to the network.

Automated checks - Level 1

Level 1 involves applying automated quality assurance procedures to the data. These include the following steps:

Burst data are loaded into memory for processing.

Calibration data for all instruments and sensors used on the deployment are retrieved from the SmartBuoy database. These may be manufacturers' sensor calibrations or the most current laboratory calibrations. Instruments are returned to the manufacturer and re-calibrated at regular intervals.

Burst data maximum and minimum ranges are checked and flagged if they fail the checks.

Burst means, result count, and result standard deviation are calculated from non-flagged burst data.

If there are data from two PAR sensors at different depths, Kd (m -1 ) is calculated for burst mean data only as LN(PAR1m/PAR2m).

Burst mean data maximum, minimum and rate of change checks are carried out and flags applied to any failures.

Time stamped burst and burst mean data with default units are stored on SmartBuoy database.

The data are now at QA status = 1.

Manual checks - Level 2

Level 1 burst mean data are now ready for manual QA procedures in order to progress to Level 2. Deployment notes are consulted for any comments on sensor performance or malfunction and post-deployment photographs of sensors, if available, are examined.

Cefas use a data visualisation tool to examine the SmartBuoy data.

A comparison is made between the end of one deployment with beginning of the next to identify possible drift and/or biofouling of OBS, Fluorometer, Salinity, PAR, and oxygen sensors.

Battery voltages are checked for sudden jumps and, if present, other sensors are examined for similar jumps to determine whether there is a problem with the sensor or if the buoy was disturbed.

Reference voltages on the FSI CT module are checked.

The standard deviation of OBS is examined. A steady increase in standard deviation is a good indication of the onset of biofouling. It is also used as a rough indicator for fluorometers during summer, except during spring, when there are large fluctuations in chlorophyll.

Li-Cor is examined for fouling, which could be indicated by a steady drop in daily maximum or a steady increase in standard deviation. If above-water Li-Cor data are available, they are used for comparison.

Pressure is examined for sudden decreases, indicating when the buoy was taken out of the water.

Roll and pitch are examined for any anomalies. It is expected that the spring/neap cycle will be present in the buoy tilt signal.

Where possible, comparison is made between burst mean data from sensors measuring the same variable. This is in order to determine whether there is a systematic offset (drift) or sensor fault and whether biofouling is present.

Comparison is made between burst mean sensor outputs from different variables as this can be helpful in determining the onset of biofouling. Any data that fail the checks are flagged with flags specific to the check that was failed.

Calibrations - Level 3

The combined information from Level 2 is used to determine the periods during which the data series are considered suspect. The data have now reached QA status = 2 and can progress to Level 3, where they will be fully calibrated with field-derived sample data.

For salinity an offset is calculated as the difference between result output from logger and the result from a discrete sample collected at the same time.

Calibration from regression analysis of field samples and logger output is applied to derive new parameters, e.g. chlorophyll calculated from fluorescence, suspended load calculated from OBS.

Chlorophyll calibrations are determined from GF/F filtered water samples, which are extracted in acetone and measured for fluorescence using a Turner Designs Fluorometer.

Suspended matter calibrations are determined from a known volume of water sample filtered through pre-weighed 0.4 µm Cyclopore filters. The filters are dried and reweighed to determine the weight of material per unit volume.

Salinity is calibrated using water samples that have been analysed with a Guildline Autosal salinometer.

Water samples from the Aqua Monitor are analysed for nutrients by colorimetric analysis of 0.4 µm Cyclopore-filtered samples.

The data have now reached QA status = 3 as time stamped, field calibrated burst mean data with parameter codes and units stored on SmartBuoy database with associated uncertainty or 95% confidence limits as appropriate. All SmartBuoy data banked at BODC have passed full Cefas QA procedures. Data that fail the Cefas QA checks are not submitted for banking.

SmartBuoy data processing by BODC

The following outlines the procedures that take place at BODC for banking Cefas SmartBuoy data.

BODC receives SmartBuoy data from Cefas after all quality checks have been passed and all possible calibrations applied. The data files are submitted as separate MS Excel spreadsheets for each parameter, i.e. there are separate files for temperature and salinity from the same instrument. An exact copy of the data is archived for safekeeping upon arrival.

Once the submitted data files are safely archived, the data undergo standard reformatting and banking procedures:

The data files are reformatted using an in-house program into a common format, which is a NetCDF subset.

Data files arising from the same instrument are combined into a single file.

Standard parameter codes are assigned that accurately describe the data.

Unit conversions are applied, if necessary, so that units are standardised. Oxygen concentration supplied by the originator in units of mg l -1 is converted to µmol l -1 by multiplying by 31.25.

The data are screened visually and any spikes or instrument malfunctions can be clearly labelled with quality control flags.

Comprehensive documentation is prepared describing the collection, processing and quality of each data series.

Detailed metadata and documents are loaded to the database and linked to each series so that the information is readily available to future users.

Sustained, systematic observations of the ocean and continental shelf seas at appropriate time and space scales allied to numerical models are key to understanding and prediction. In shelf seas these observations address issues as fundamental as 'what is the capacity of shelf seas to absorb change?' encompassing the impacts of climate change, biological productivity and diversity, sustainable management, pollution and public health, safety at sea and extreme events. Advancing understanding of coastal processes to use and manage these resources better is challenging; important controlling processes occur over a broad range of spatial and temporal scales which cannot be simultaneously studied solely with satellite or ship-based platforms.

Considerable effort has been spent by the Proudman Oceangraphic Laboratory (POL) in the years 2001 - 2006 in setting up an integrated observational and now-cast modelling system in Liverpool Bay (see Figure), with the recent POL review stating the observatory was seen as a leader in its field and a unique 'selling' point of the laboratory. Cost benefit analysis (IACMST, 2004) shows that benefits really start to accrue after 10 years. In 2007 - 2012 exploitation of (i) the time series being acquired, (ii) the model-data synthesis and (iii) the increasingly available quantities of real-time data (e.g. river flows) can be carried out through Sustained Observation Activity (SO) 11, to provide an integrated assessment and short term forecasts of the coastal ocean state.

Overall Aims and Purpose of SO 11

To continue and enlarge the scope of the existing coastal observatory in Liverpool Bay to routinely monitor the northern Irish Sea

To develop the synthesis of measurements and models in the coastal ocean to optimize measurement arrays and forecast products. Driving forward shelf seas' operational oceanography with the direct objective of improving the national forecasting capability, expressed through links to the National Centre for Ocean Forecasting (NCOF)

To exploit the long time-series of observations and model outputs to: a) identify the roles of climate and anthropogenic inputs on the coastal ocean's physical and biological functioning (including impacts of nutrient discharges, offshore renewable energy installations and fishing activity) taking into consideration the importance of events versus mean storms / waves, river discharge / variable salinity stratification / horizontal gradients; b) predict the impacts of climate change scenarios; and c) provide new insights to Irish Sea dynamics for variables either with seasonal cycles and interannual variability, or which show weak or no seasonal cycles

To provide and maintain a 'laboratory' within which a variety of observational and model experiments can be undertaken (Oceans 2025 Themes 3, 6, 8, 9), including capture of extreme events

Demonstrate the value of an integrated approach in assessment and forecasting

Demonstrate the coastal observatory as a tool for marine management strategies through collaboration with the Environment Agency (EA), Department for Environment, Food and Rural Affairs (DEFRA), Joint Nature Conservation Commmittee (JNCC), English Nature (EN), Department of Agriculture and Rural Development (DARD), and Local Authorities, providing management information pertinent to policy (e.g. Water Framework Directive)

Smartbuoy deployment LB1_052 / POLRIG#1043

Deployment and Recovery

This SmartBuoy rig was deployed in a collaboration between Cefas and POL at Liverpool Bay Coastal Observatory Site A. Recovery was planned to take place during October cruise PD33_08, however poor weather conditions during the cruise meant that recovery was postponed until the December cruise, PD37_08.

Rig Description

The Cefas SmartBuoy carried a suite of instruments mounted just below the surface, as well as instrumentation belonging to POL at between 5 and 15 metres below the surface. The frame was also fitted with bags for the determination of bacterial degradation. The single point mooring was composed mainly of 1/2" long link chain, marked by a 1.8 m diameter toroid and anchored by a half tonne clump of scrap chain. Further information about the instrument suite is given in the table below.

Fixed Station Information

Station Name

COA

Category

Offshore area

Latitude

53° 31.51' N

Longitude

3° 23.00' W

Water depth below MSL

26.0 m

Liverpool Bay Coastal Observatory Mooring Site A (COA/Site 1/Site 9)

This station is the main mooring site for the Proudman Oceanographic Laboratory (POL) Liverpool Bay Coastal Observatory and was first occupied in 2002. It is also known both as Coastal Observatory Site 1 and Site 9. POL perform two main types of activities at this station: they deploy moorings; and in addition, they take CTD profiles during each site visit. The station lies within a box of mean water depth 22.5 m with the following coordinates:

Box Corner

Latitude (+ve North)

Longitude (+ve East)

North-west corner

53.54097

-3.42958

South-east corner

53.50945

-3.33714

The position of this station relative to the other POL Coastal Observatory sites can be seen from the figure below.